\begin{tikzpicture}
    \tkzDefPoints{0/0/B, 3/0/C, 2.3/2/A}
    \tkzDefLine[altitude](A,B,C)  \tkzGetPoint{E}
    \tkzDefLine[altitude](A,C,B)  \tkzGetPoint{F}

    \tkzDrawPolygon(A,B,C)
    \tkzDrawSegments(B,E  C,F)
    \tkzMarkRightAngle[size=.2](B,E,C)
    \tkzMarkRightAngle[size=.2](B,F,C)
    \tkzLabelPoints[above](A)
    \tkzLabelPoints[left](B)
    \tkzLabelPoints[right](C,E)
    \tkzLabelPoints[above](F)
\end{tikzpicture}

